Mangrove pneumatophore roots a. prop the trees up above the water line b. excrete excess salt c. absorb carbon dioxide from the air d. none of the above

Correct A). Prop the trees up above the water line

The mangrove pneumatophore is the root structure that commonly grows out of the water and help to provide oxygen to the plants.

It mainly found in mud where the conditions are anaerobic means lack of oxygen. Oxygen is necessary for their survival that is done by the mangrove pneumatophore roots.  

Hence, the most suitable answer would be option A.

answer:

the water molecules are transferred from the roots to the stem or top parts of the tall tree because of important properties of water which are adhesion, cohesion and capillary action. cohesion is the property of water molecules keeps water molecules in a combined state by sharing of bonds between them at the atomic level. adhesion allows the interaction of water molecules with other substances or substrate. adhesion will cause the attachment of water molecules to the wall of the vessel (xylem) of the plant. capillary action occurs when the adhesive force to the vessel wall is stronger than the cohesive force between water molecules. capillary action mimics the transfer of water from a tube or pipe. in this way water utilizes its property to transfer water from down to top level of the plant.  

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.